In the construction of computers, computer chips are often mounted on substrates, such as ceramic substrates. The substrates are, in turn, plugged into a printed circuit board by means of pins which are fixed into holes in the substrate and normally extend at right angles to the plane of the substrate. The pins are plugged into sockets in the printed circuit board.
Printed circuit lines on the substrate connect the electrically conductive computer chip with the pins. The pins are normally made of a conductive material, as are the sockets on the printed circuit board. A printed circuit on the printed circuit board enables electrical communication between the computer chip and other components of the computer through this conductive path.
The fixing of pins in the substrate is an important aspect in the manufacture of the substrate. It is desirable in many computer applications to have the pins fixed or retained in the substrate by heading and bulging.
Heading and bulging is a cold forging technique in which a pin is first inserted through a hole in a substrate so that a short portion of the pin extends beyond one side of the substrate and a long portion of the pin is held in a fixture on the other side of the substrate. The short portion of the pin is impacted with a hammer mechanism. The impact causes the short portion of the pin to forge into a head shape, causes the portion of the pin in the hole to fill the hole, and causes a bulge to form in the long portion of the pin between the fixture and the substrate. The pin is retained in the substrate by the head and the bulge and by the tight fit of the pin in the hole.
Heading and bulge of the pin by impacted is widely used in the computer industry with success. However, there are accompanying problems and difficulties. The pin hammer mechanism is complex and requires high energy input. It often requires a great deal of energy to remove the long portions of the pins from the fixture after impacting.
An apparatus for automatically inserting electrical contacts into an electrical connector is described in U.S. Pat. No. 4,356,626 to Waghorn. Waghorn's apparatus uses air pressure to move contacts along a passageway and to insert the contacts in a connector where they are retained by press fit. Waghorn does not provide assistance in a search for an improved method for heading and bulging pins in a substrate.
Canadian Patent No. 891,180 to International Business Machines Corporation describes a method for making small through holes in a laminated circuit board by projecting a projectile through the board at high speed. This patent provides no assistance to one looking for an improved method for heading and bulging pins in a substrate.